As image display devices, LCDs, touch panel-equipped LCDs, ELs, electronic paper, and the like have been rapidly distributed in recent years in place of CRT displays of the related art due to their characteristics of power saving, lightweight, large thickness, and the like.
For optical laminated bodies used on the surfaces or in the inside of the image display devices, generally, there is a demand for imparting hardness so as to prevent the optical laminated bodies from being scratched while being handled and thus it is common to impart hardness by providing a hard coat layer or the like onto a light-permeable base material. For example, in LCDs, it is common to impart hardness to image display surfaces by using a hard coat film in which a polarization element is disposed on a side facing the image display surface of a liquid crystal cell and a hard coat layer is provided on a light-permeable base material as a polarization plate protective film.
In the related art, as the light-permeable base material for the hard coat film, films made of a cellulose ester represented by triacetyl cellulose have been used. This has been based on an advantage that cellulose esters have excellent transparency and optical isotropy and rarely have a phase difference in the plane (have a low retardation value) and thus rarely change the vibration direction of straight incident polarized light and have a little influence on the display quality of liquid-crystal display devices or an advantage that cellulose esters have appropriate water permeability and thus are capable of drying any moisture remaining in a polarizer when a polarization plate formed using an optical laminated body is manufactured through the optical laminated body.
However, cellulose ester films are materials having disadvantages in terms of cost, have insufficient humid resistance and heat resistance, and have a defect of degrading polarization plate functions such as a polarization function or hue when a hard coat film including the cellulose ester film as a base material is used as the polarization plate protective film in a high-temperature and humidity environment.
Due to the above-described problems of the cellulose ester films, the use of transparent plastic base materials including an acrylic resin as a main component which have excellent transparency, humid resistance, heat resistance, and mechanical strength and can be easily procured from the market at a lower price compared with the cellulose ester films has been proposed.
However, in optical laminated bodies in which hard coat layers are formed on either or both surfaces of a base material including an acrylic resin as a main component, there has been a problem of poor adhesiveness between the acrylic base material and the hard coat layer. In addition, there has been another problem in that an interference pattern is generated and thus the appearance becomes poor due to the refractive index difference between the acrylic base material and the hard coat layer.
With respect to the above-described problems, for example, PTL 1 discloses that the adhesiveness between a base material film and a hard coat layer is improved by applying paint called an anchoring agent or a primer to a base material film in addition to a physical treatment such as a corona discharge treatment or an oxidization treatment and then forming a hard coat layer. In addition, for example, PTL 2 discloses a method in which, regarding the prevention of the interference pattern, protrusions and recesses are formed on the interface between a base material film and a hard coat layer.
However, in the above-described methods, the number of steps necessary to manufacture the hard coat film increases and it is necessary to carry out special treatments and thus the productivity deteriorates.